An increasing number of emerging Internet applications require better than best effort quality of service (QoS) that is offered by the current Internet. Applications such as voice over IP (VoIP), video on demand (VoD) and e-commerce applications need end-to-end QoS guarantees defined in terms of throughput, delay and loss rate [1]. However, QoS guarantee for these services require adding QoS algorithms that perform a number of resource management functions such as admission control, resource reservation and traffic monitoring. These functions can significantly increase the complexity and affect the scalability of the network. In this paper, three QoS schemes, integrated services (IntServ) [2], differentiated services (DiffServ) [3] and IPv6 QoS management, are compared with respect to QoS guarantee requirements. Also, the scalability and complexity issues are discussed for each one of them. The IPv6 QoS management model [4] performs well during the simulation. It is also simple and scalable when it is implemented.